At Wed, 13 May 2015 22:39:03 +0800, Koro Chen wrote:

Currently in snd_pcm_update_hw_ptr0 during interrupt, we consider there were double acknowledged interrupts when:

1. HW reported pointer is smaller than expected, and
2. Time from last update time (hdelta) is over half a buffer time.

However, when HW reported pointer is only a few bytes smaller than expected, and when hdelta is just a little larger than half a buffer time (e.g. ping-pong buffer), it wrongly treats this IRQ as double acknowledged.

The condition #2 uses jiffies, but jiffies is not high resolution since it is integer. We should consider jiffies inaccuracy.

Signed-off-by: Koro Chen koro.chen@mediatek.com

The condition looks too strict, indeed. I applied the patch as is now.

BTW, the similar check is already present for the free-wheeling case. I'm going to clean up the code a bit for using the common code.

thanks,

Takashi

---

sound/core/pcm_lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index ac6b33f..7d45645 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -339,7 +339,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, if (delta > new_hw_ptr) { /* check for double acknowledged interrupts */ hdelta = curr_jiffies - runtime->hw_ptr_jiffies;

• 	if (hdelta > runtime->hw_ptr_buffer_jiffies/2) {
  

• 	if (hdelta > runtime->hw_ptr_buffer_jiffies/2 + 1) {
  	hw_base += runtime->buffer_size;
  	if (hw_base >= runtime->boundary) {
  		hw_base = 0;
  

-- 1.8.1.1.dirty